A standard x-ray imaging film comprises a substrate foil or sheet typically made of a polyester or other durable synthetic resin and carrying a layer of a phosphor stimulable by x-ray radiation. Once exposed such a film is held in an apparatus that can read the exposure, usually using laser technology. Thereafter the phosphor is restored so that the film can be reused.
As a rule the x-ray film is held in a cassette which is transparent to x-radiation and in which it is exposed so that it carries a latent image. A reading device such as described in German patent document Nos. 3,731,203 and 3,731,204 can stimulate the phosphors to bring out the image which is then scanned and converted into digital signals that can be viewed on a monitor or converted into a viewable or printable image. The image is then erased and the film is put back into its cassette. It is normal also for the x-ray film sheet to also carry indicia identifying the patient, the exposure date, and the like, and this indicia is also read and then erased before reuse of the film.
Such a film is reusable, but must be handled substantially each time it is used. It must be taken out of its cassette, loaded into the reader, positioned therein on a handling station, and thereafter taken out of the reader and returned to its cassette. Invariably the sensitive phosphor face of the film is touched and, inevitably, worn and scratched.
Even though the systems of the above-cited patent documents use a cassette to hold the film sheet except when it is in the reader, the film is subjected to considerable mechanical action as it is taken from and put back into the cassette. Thus it is standard to only reuse such a valuable x-ray film 2000 to 3000 times. After this much use the phosphors still have sufficient life for many more uses, but the phosphor side of the film is too scratched or otherwise mechanically damaged for reuse.